For colored thread: Irish moss, 3 pounds; gum arabic, 2.5 pounds; Japan wax, 0.5 pound; stearine, 185 grams; borax, 95 grams; boil together for 0.25 hour.

For white thread: Irish moss, 2 pounds; tapioca, 1.5 pounds; spermaceti, 0.75 pound; stearine, 110 grams; borax, 95 grams; boil together for 20 minutes.

For black thread: Irish moss, 3 pounds; gum Senegal, 2.5 pounds; ceresin, 1 pound; borax, 95 grams; logwood extract, 95 grams; blue vitriol, 30 grams; boil together for 20 minutes. Soak the Irish moss in each case overnight in 45 liters of water, then boil for 1 hour, strain and add the other ingredients to the resulting solution. It is of advantage to add the borax to the Irish moss before the boiling.

Tin Formulas

Etching Bath for Tin

The design is either freely drawn upon the metal with a needle or a lead pencil, or pricked into the metal through tracing paper with a needle. The outlines are filled with a varnish (wax, colophony, asphalt). The varnish is rendered fluid with turpentine and applied with a brush. The article after having dried is laid in a 0.5 solution of nitric acid for 1.5 to 2 hours. It is then washed and dried with blotting paper. The protective coating of asphalt is removed by heating. The zinc oxide in the deeper portions is cleaned away with a silver soap and brush.

Recovery of Tin and Iron in Tinned-Plate Clippings

The process of utilizing tinned-plate scrap consists essentially in the removal of the tin. This must be very completely carried out if the remaining iron is to be available for casting. The removal of the outer layer of pure tin from the tinned plate is an easy matter. Beneath this, however, is another crystalline layer consisting of an alloy of tin and iron, which is more difficult of treatment. It renders the iron unavailable for casting, as even 0.2 per cent of tin causes brittleness. Its removal is best accomplished by electrolysis. If dilute sulphuric acid is used as an electrolyte, the deposit is spongy at first, and afterwards, when the acid has been partly neutralized, crystalline. After 6 hours the clippings are taken out and the iron completely dissolved in dilute sulphuric acid; the residue of tin is then combined with the tin obtained by the electrolysis. Green vitriol is therefore a by-product in this process.

Gutensohn's process has two objects: To obtain tin and to render the iron fit for use. The tin is obtained by treating the tinned plate repeatedly with hydrochloric acid. The tin is then removed from the solution by means of the electric current. The tinned plate as the positive pole is placed in a tank made of some insulating material impervious to the action of acids, such as slate. A copper plate forms the cathode. The bichloride of tin solution, freed from acid, is put round the carbon cylinder in the Bunsen element. Another innovation in this process is that the tank with the tinned-plate clippings is itself turned into an electric battery with the aid of the tin. A still better source of electricity is, however, obtained during the treatment of the untinned iron which will be described presently. The final elimination of the tin takes place in the clay cup of the Bunsen elements. Besides the chloride of tin solution (free from acid), another tin solution, preferably chromate of tin, nitrate of tin, or sulphate of tin, according to the strength of the current desired, may be used. To render the iron of the tinned plate serviceable the acid is drawn off as long as the iron is covered with a thin layer of an alloy of iron and tin. The latter makes the iron unfit for use in rolling mills or for the precipitation of copper. Fresh hydrochloric acid or sulphuric acid is therefore poured over the plate to remove the alloy, after the treatment with the bichloride of tin solution. This acid is also systematically used in different vats to the point of approximate saturation. This solution forms the most suitable source of electricity, a zinc-iron element being formed by means of a clay cell and a zinc cylinder. The electrical force developed serves to accelerate the solution in the next tank, which contains tinned plate, either fresh or treated with hydrochloric acid. Ferrous oxide, or spongy metallic iron if the current is very strong, is liberated in the iron battery. Both substances are easily oxidized, and form red oxide of iron when heated. The remaining solution can be crystallized by evaporation, so that ferrous sulphate (green vitriol) or ferric chloride can be obtained, or it can be treated to form red oxide of iron.

Tin in Powder Form

To obtain tin in powder form the metal is first melted; next pour it into a box whose sides, etc., are coated with powdered chalk. Agitate the box vigorously and without discontinuing, until the metal is entirely cold. Now pass this powder through a sieve and keep in a closed flask. This tin powder is eligible for various uses and makes a handsome effect, especially in bronzing. It can be browned.